For example, a rolling bearing such as an angular ball bearing is used for supporting rotating shafts at a comparatively high speed such as various spindles to be used in a machine tool. As a lubricating method for the rolling bearing to support the high-speed rotating shafts, conventionally, an oil air lubricating method has mainly been used often.
In the oil air lubricating method, a very small amount of lubricating oil supplied intermittently is sprayed toward the rolling bearing by compressed air through a pipe. In order to break through an air curtain formed around the rolling bearing rotated at a high speed to supply the lubricating oil to the bearing, the compressed air is used as a so-called carrier. FIG. 19 is a view including a sectional view illustrating an example of a structure of a spindle using the lubricating method and a block diagram illustrating an example of a structure of an external device for lubrication.
This example represents a lubrication for a spindle 21 which rotatably supports a rotating shaft 312 by means of four angular ball bearings 313 in a housing 311, an oil air lubricating device 22 includes a lubricating oil tank and a pump for supplying lubricating oil in the tank to a plunger for supplying a certain amount of lubricating oil in addition to the plunger, and the lubricating oil supplied from the oil air lubricating device 22 and compressed air obtained by cleaning compressed air sent from a compressor 23 by means of an air clean unit 24 are mixed by means of a mixing valve 25 and the mixture is supplied to the spindle 21 through a pipe 26. In the spindle 21, a hole 331 for an oil air lubrication is formed on the housing 311 corresponding to each angular ball bearing 313, and furthermore, a hole 332 having one of ends communicating with the hole 331 of the housing 21 and the other end opposed to an annular-shaped space between an inner ring 313a and an outer ring 313b in the angular ball bearing 313 is also formed on a spacer 314 fixed adjacently to a fixed ring of the angular ball bearing 313, that is, the outer ring 313b in this example. A nozzle 333 is provided in an opening portion facing an annular-shaped space of the hole 332 and oil air is jetted from the nozzle 333.
In the oil air lubricating method, it is necessary to provide an oil air lubricating device, a mixing valve, a compressor and an external pipe on the outside of the spindle, and furthermore, to form a passage for the oil air in the spindle. Consequently, a cost is increased. In addition, there is also a problem in that a noise level is increased because the compressed air is used.
In order to solve such a problem, there has been proposed a rolling bearing device in which a lubricating oil supply mechanism is provided in a rolling bearing (for example, see Patent Document 1).
In the proposed technique, as shown in an axial sectional view of FIG. 20, an oil feeding unit comprising a tank 35 for storing lubricating oil, a pump 36 for sucking and discharging the lubricating oil in the tank 35, a nozzle 37 attached to a discharge port of the pump 36 and extended to the vicinity of rolling elements 33 in an annular-shaped space between an inner ring 31 and an outer ring 32 is fixed to a seal 34 fixed to a fixed ring of a rolling bearing having main components of the inner ring 31, the outer ring 32 and the rolling elements 33, for example, the outer ring 32, and the lubricating oil in a very small amount of approximately several tens nl (several tens μcc) is dropped into an inside of an air curtain formed during the rotation of the rolling bearing through a tip of the nozzle 36.
According to the proposed technique, it is not necessary to provide devices and pipes on the outside of the spindle for carrying out an oil air lubrication over the rolling bearing. Moreover, it is not necessary to form a passage for the oil air lubrication in the spindle and it is also possible to solve the problems of noises because of non-use of the compressed air.
Patent Document 1: JP-A-2004-108388
Patent Document 2: JP-A-2004-316707